Question 1

What is a reverse DNS (PTR) record?

Accepted Answer

A PTR record maps an IP address back to a hostname — the inverse of a normal forward A/AAAA record. It is published in the in-addr.arpa (IPv4) or ip6.arpa (IPv6) zone by whoever controls the IP block, typically the hosting provider or ISP.

Question 2

Why does reverse DNS matter for email deliverability?

Accepted Answer

Most production mail servers reject or score down inbound mail from IPs without matching PTR records. Forward-confirmed reverse DNS (FCrDNS) — where the PTR hostname resolves back to the same IP — is required by many large mailbox providers, including Google and Microsoft.

Question 3

Who controls the PTR record for an IP?

Accepted Answer

The PTR record is delegated by the IP block owner, not the domain owner. For a leased VPS or cloud IP, the hosting provider (AWS, DigitalOcean, Hetzner, etc.) sets it — usually through their control panel. You cannot set a PTR for an IP you do not control.

Question 4

Why does an IP have no PTR record?

Accepted Answer

Residential, mobile, or freshly provisioned IPs often have no PTR set, or a generic provider-default. This is normal but signals consumer connectivity to anti-spam systems, which is why home connections cannot reliably send transactional email.

Question 5

Can one IP have multiple PTR records?

Accepted Answer

Technically yes, but it is discouraged. Multiple PTRs confuse FCrDNS validation and reverse-lookup tooling. Best practice is exactly one PTR per IP, matching the primary hostname.

DNS records lookup